1. Field of the Invention
The present invention relates to a key device, and more particularly, to a key device having a scissors mechanism.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a diagram of a key device 10 according to the prior art of U.S. Pat. Nos. 5,278,371, 5,746,308. FIG. 2 is a section view 2xe2x80x942 of the key device 10 according to the prior art. The key device 10 comprises a keycap 12, a base plate 14, a rubber dome 16 for supporting the keycap 12 elastically, and a corresponding signal sensor 17 on an upper surface 18 of the base plate 14. An inner part of the rubber dome 16 comprises a contact strip 19 for triggering the signal sensor 17, and then producing a corresponding signal while the keycap 12 is depressed to a predetermined position.
While the keycap 12 is depressed, the keycap 12 will return to an original position due to an elastic restoring force of the rubber dome 16. After using the keycap 12 for a long period of time, the rubber dome 16 will become elastically fatigued, and the keycap 12 can not return to the original positionanymore, that is, the life of the keycap 12 will be reduced.
Furthermore, the above-mentioned design is very difficult to reduce a distance between the keycap 12 and the base plate 14 under limits of materials and shape of the rubber dome 16, and leads to a condition of insufficient spring force or bad touching feeling. With a movement toward smart notebook PCs, the prior art design can not conform to current requirements.
It is therefore a primary objective of the claimed invention to provide a key device with an elastic scissors device, which can adjust the elastically restoring force and have a lower height of keycap, and can operate for a long time to increase the life of the key device.
The claimed invention includes a key device comprising a base plate, a keycap set above the base plate, a scissors mechanism disposed between the base plate and the keycap, and an elastic component has a first end and a second end. The scissors mechanism comprises a first supporting arm and a second supporting arm for forming the scissors mechanism in an intersecting manner. The first end of the elastic component is connected to the base plate,and the second end of the elastic component is connected to the first supporting arm, and forming a first angle, of less than 90 degrees, between the base plate and the elastic component. While the keycap is depressed, the keycap moves downward with the second end of the elastic component, and the elastic component rotates around the first end of the elastic component to decrease the first angle. Then the elastic component is stressed and deformed to support an upward spring force of the keycap.
It is an advantage of the claimed invention that it can decrease the height of the keycap of the key device and not have the condition of elastic fatigue after using the key device for a long time. Furthermore, it can be designed to adjust freely the relationship between the downward displacement and the depressed force to conform to the needs of different conditions.
These and other objectives and the advantages of the claimed invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.